Philippe Glaziou has a sample size calculator (sampsize) for Linux / Unix. Features include finite population correction, exact methods to compute the sample size required to observe a minimum number of events, sample size and power for one-sample and two-sample comparative studiess, correction for complex sampling designs, sample size and power of unmatched and matched case-control studies, minimum and maximum detectable odds-ratio of case-control studies. This is a command line program. A web-interface (written in perl) is provided and is implemented here.